1. Field of the Invention
The present invention relates generally to the operative treatment of the distal radio-ulnar joint and more particularly to the restoration of painfree rotation of the forearm and stability of the ulna and wrist by means of a soft tissue repair combined with a reconstruction of the triangular fibro-cartilage complex.
2. Relevant Background
The distal radio-ulnar joint consists of a shallow "ball and socket" articulation between the head of the ulna and the sigmoid fossa of the radius (FIG. 1a). This articulation allows for 180.degree. of forearm rotation which is essential for normal function of the hand. The triangular fibro-cartilage complex acts as a cushion between the head of the ulna and the proximal row of the carpus. By means of its strong soft tissue attachments to the apex of the ulnar head and the capsule of the distal radio-ulnar joint, it is also the major stabiliser of the distal radio-ulnar joint. Similarly, its distal expansions merge with the wrist capsule to stabilise the ulnar side of the carpus on the wrist. It allows for a free range of flexion, extension, ulnar deviation at the ulno-carpal joint.
Disorders of the distal radio-ulnar joint are common and usually associated with pain, weakness, instability and loss of forearm rotation. Any loss of congruity between the sigmoid fossa of the radius and the ulnar head will result in painful loss of forearm rotation. Causes include congenital abnormalities such as Madelung's deformity, radial fractures, inflammatory arthritis and tears of the triangular fibro-cartilage complex. Tears of the triangular fibro-cartilage complex are extremely common, particularly in patients with ulnar plus variance. Tears may be due to acute or chronic trauma, and leads to pain and loss of motion in the ulnar side of the wrist. The loss of integrity of the triangular fibro-cartilage complex results in instability of both the distal radio-ulnar joint and the ulno-carpal joint which is likely to result, in time, in a fixed deformity leading to a secondary osteoarthritis. If normal alignement between the distal radius and ulna is lost an "ulnar plus" deformity will increase to the extent that the ulna starts to impact on the lunate and/or triquetrum. This impaction may result in triquetro-lunate instability and ulno-carpal osteoarthritis.
The most common cause of these problems is fracture of the distal radius. This may be associated with avulsion fracture of the ulnar styloid process, leading to fractional instability of the triangular fibro-cartilage complex. More commonly radial malunion results in a secondary ulnar plus deformity. Occasionally direct damage to the sigmoid fossa may lead to the development of secondary osteoarthritis.
Furthermore, trauma may result in acute dislocation of the distal radio-ulnar joint itself, often in association with radial head fracture and tear of the interosseous membrane.
Other conditions affecting the distal radio-ulnar joint and triangular fibro-cartilage complex include growth disorders (Madelung's deformity), primary osteoarthritis, metabolic disorders (e.g. gout), rheumatoid arthritis.
Finally, many patients suffer from painful instability following previous surgical procedures on the distal radio-ulnar joint.
Several prior art operative procedures exist regarding the removement of disorders of the distal radio-ulnar joint.
Darrach's procedure comprises the excision of the ulnar head and thus destabilises the triangular fibro-cartilage complex leading to ulno-carpal and radio-ulnar instability often resulting in painful radio ulnar impingement (FIG. 1b).
Bowers procedure attempts to overcome the above-mentioned problems by preserving the attachment of the triangular fibro-cartilage complex to the ulnar styloid process, thus retaining some stability (FIG. 1c). However, soft tissue interposition between the sigmoid fossa and the resected surface of the ulna is seldom strong enough to prevent some degree of ulno-carpal and radio-ulnar instability, due to loss of the normal alignement between the radius and the ulna. Furthermore, in cases of ulnar plus variance, ulno-carpal impaction will occur unless the ulna is shortened at the same time.
Another surgical treatment is the Sauve-Kapandji procedure (FIG. 1d) which relieves any ulno-carpal impaction whilst maintaining function of the triangular fibro-cartilage complex if performed correctly. However, rotation is only restored at the expense of an unstable ulnar pseudoarthrosis which commonly results in painful radio-ulnar impingement. Furthermore, exact positioning of the radio-ulnar fusion is difficult which may lead to ulno-carpal impaction and triangular fibro-cartilage complex problems.
To prevent radio-ulnar instability following ulnar head resection silastic ulnar head replacement was designed (Swanson, FIG. 1e). With modifications it may also allow for reconstruction of the triangular fibro-cartilage complex and restoration of ulno-carpal instability. However, the silastic prosthesis is subject to excessive wear which may be complicated by the development of silicone synovitis. As a result many of these prostheses have had to be removed resulting in painful ulno-carpal instability.
Although any of the above procedures may produce reasonable results if correctly carried out and in appropriate patients, there are, however, many patients who are discontented with the results of surgery and who are seeking a suitable revision procedure to restore stability and painfree rotation at the distal radio-ulnar joint. None of the above-mentioned prior art operative procedures comprises a surgical treatment which can be guaranteed to restore painfree rotation and at the same time correct any underlying instability of length discrepancy.
It is therefore the object of the present invention to provide a new operative procedure for restoration of the distal radio-ulnar joint which, combined with a careful reconstruction of the triangular fibro-cartilage complex and the use of a ulnar based capsulo-retinacular flap, results in stability and painfree rotation.